1. Technical Field
The present invention relates to image processing performed in the case of performing color display using four colors of sub-pixels.
2. Related Art
As an arrangement of pixels in a display device using three primary colors, there can be cited a stripe arrangement and a delta arrangement (see, e.g., JP-A-07-006703 (Document 1)). In such a display device, each pixel is composed of three sub-pixels. Besides these arrangements, there is known the Bayer arrangement. In the Bayer arrangement, one pixel is composed of totally four sub-pixels arranged 2×2 including two G (green) sub-pixels, one R (red) sub-pixel, and one B (blue) sub-pixel.
In the display device using the Bayer arrangement, color display is generally performed using image data with the number of pixels a quarter of the number of pixels of image data input thereto. In this case, the resolution of the image data used actually is lower than the resolution of the image data input thereto. Therefore, in order to suppress the moire caused by folding noise, a filter process for limiting a frequency band of an image signal is performed. For example, in the case of R and B image signals, in order for preventing moire caused by a high-frequency component, it is necessary to limit the frequency band of both of the vertical and lateral directions to a half (i.e., ½) thereof. It should be noted that since a G image signal has twice as many sub-pixels as the R or B image signal, the limitation range of the band can be smaller than those of the R and B image signals.
There is a case in which the color display is performed using four primary colors (or more primary colors) for the purpose of improvement of color reproducibility and brightness. For example, JP-A-2006-267541 (Document 2) discloses an image display device having either one of the G sub-pixels in the Bayer arrangement replaced with a white (W) or a cyan (C) sub-pixel to thereby perform the color display with four colors of sub-pixels. Further, JP-A-2000-338950 (Document 3) discloses a technology for calculating color image signals of the respective colors in the case of having a color display section of four or more primary colors. It should be noted that the “primary color” mentioned here denotes the color forming a base of the color mixture (an additive process), and is not limited to the light's three primary colors.
In the case of performing the color display using the four colors of sub-pixels, if the band of the image signal is limited independently color by color, moire or false color may occur in some cases.